I've always wanted to feel like Frodo on Amon Hen, seeing all the way to Barad-dûr, ect. Sadly, Minecraft does not support seeing this far. However, i've come up with an Idea how this can be implemented without totally toasting your PC. Without further ado, here's the Idea: A custom skybox, wich enables once you reach a certian height in a certain Biome, for Example the height on wich you'd recieve the Mountaineer achievement (Above the Cloud Layer) in the Wind mountains biome. However; this would require another texture for the skybox for every 16 chunks or so, since the perspective changes. To change this there could be differend Points from wich one could see afar, for Example Minas Tirith, Barad-dûr, Amon Hen, Amon Sul (If rebuilt) and Erebor. This is better than the previously named method because it would only require different textures for the different Points.
EDIT: The skybox would show the Major builds (Even if they're not there yet), and the Different Biomes